Charles hugh duffy



C H. DUFFY.

SPARK PLUG. APPLLCATION FILED MAR. 13 1920.

Beissued May 25, 1920., 14,862.

13-? wavy/0r a shoulder 11' to receive the insulating core.

in the manner as shown in Fig. 1 ;,.wh1le the gland 4 of the shell is provided with'an inwardly extending annular portion 12 to engage the insulating core in the manner as shown inthe drawing, the said gland 4 bein provided with an opening 13 sufficiently large to permit of the said gland passing freely over the outer portion of the insulating' core. I

14 indicates the insulating core of the plug which may be constructed of any suitable heat resisting insulating material, the same being preferably shaped in the manner as illustrated in Fig. 1, the extreme upper por-' tion being'preferably swelled as illustrated at 15, the core being provided at substan tially the center thereof with an enlargement 16 providing'suitable shoulders 17 and 18 for engagement with the body portion and gland of the' shell.

19 indicates-the lower inclosed portion of the insulating core, said lower inclosed portion being provided with a plurality of annularchambers 20, while a plurality of annular'webs or'fianges 21 is formed on the lower inclosed portion of the insulating core by reason of the annular chambers 20, the samebein'g preferably arranged in the manner as shown in Fig. 1. About midway of the insulating core is provided a small central longitudinal bore 22,. while the lower inclosed'portion of the insulating core is provided with a relatively large central bore 2 3 crossing the planes of the annular chambers 20, thus forming an annular insulating wall spaced from and ou central electrode. The upper exposed portion of the insulating core is provided with a relatively large central bore 24, said bores 23 and 24 communicating with the small central bore 22, thereby forming a shoulder aboveand below the said small central bore 22 in the manner as shown in the drawing.

25 indicates the upper threaded portion of the central electrode 26, said central electrode 26 being provided'with a swell 2 7 or with a small threaded nut, said swell or small threaded nut 27 being of a size to enter the large'bore 23 in the lower inclosed portion of the insulating core and to engage the shoulder below the small central bore 22 in the manner as shown in Fig. 1; a suitable gasket or other packing means can be employed to prevent leakage through the insulating 'core in the usual manner.

t of contact with the 28 indicates the upper portion of the central electrodewhich asshown in the drawing, is provided with a lower enlarged portion 29, said portion 29 being of a size to enter the large bore 24 in the upper portion of the insulating core, the said enlarged portion 29 being internally threaded to receive the threaded end 25 of the,lower electrode being provided above the annular flange 31 to receive a wire terminal, the extreme upper end of the portion 28 being headed at 33 to provide a finish for this portion, the secondary wire terminal being held between the head 33 and the annular flange 31 in the manner which will be apparent from an inspection of the accompanying drawing.

The extremelower end of the central electrode 26 is provided with a long and relatively narrow longitudinal slot 34, the lower electrode 10 approaching the central electrode 26 at the slotted end thereof so as to provide a spark-gap 35 between the said two electrodes, the relative position of the electrodes being further illustrated in Figs. 2 and 3.

Referring now to Fig. 4, which illustrates a modification of the construction just described, it will be seen that the lower electrode 10 is provided with a long and relatively narrow slot 34 cut into the outside of the wall of the electrode and extending longitudinally of the electrode, the central electrode 26 approaching the said slot 34 in the electrode 10, preferably intermediate the ends of the ground electrode 10 to provide a suitable spark gap between the center electrode and the slot 34 in the ground electrode 10.

In Fig. 5 the lower electrode 10 is curved in the manner as lllustrated, the curved end of the electrode being provided with a Mug and relatively narrow slot 34 extending below the spark gap, the'end of which approaches the central electrode 26 to provide i with the end or sides of the said capillary races capillary slot or cut, a capillary attraction is provided for any liquid coming in contact slot or cut. Consequently when the fellow electrode is properly positioned with re spect to the said slot or cut, any liquid bridging the spark gap will be drawn into the capillary slot or cut by capillary attraction.

'As will appear from the accompanying drawing, the slot or out which may be formed in either oneofthe electrodes is arranged longitud' ally of the electrode and is open from en toend, although it is not essential to the proper operation of thisdevice ,that1the slot, or cut extend entirely through thaelectrode, as the capillary action place-even though the slot or out 113: closed, or even though the slot or. cutlsimply'extends partially through the electrode and not entirely acrossthe same, it being of course understood that the exact shape or ,form of the cut or slot is immaterial as far as any capillary action is concerned, it simply being essential that the slot or cutbe of a capillary size so as to attract li uid therein. 9

v eferring now-to the construction of the body portion of the central electrode, it will be -seen that only the relatively short threaded portion 25 of the central electrode is clamped within the insulating core. Consequently the expansion and contraction. of this relatively short piece of metal is quite negligible, as it allows the entire lower inclosed portion of the insulator to freely expand and contract, while the upper portion of the insulator is equally free to expand andcontract unhainpered by the central electrode, and it is obvious that both the lower and upper portions of the metal electrade are free to expandrandvcontract with- "out clamping or placing upon the insulator any undue stress or strain which would tend to injure the same. The central threaded portion of the central electrode is preferably cemented within the insulator to insure a gas-tight construction and to pre the electrode within the insulator.

Referring now to the insulator, it will be I seen that the lower inclosed portion thereof,

which is provided with annular chambers 20', is of a .size which provides an annular space or chamber surrounding the lower in closed portion otthe insulator-and between said portion and the inner wall of the metal shell of the plug; while it will be seen that the said lower inclosed portion of the insulator is of a circumference in excess of the lower bore or chamber 7 of the plug, l'ly reason oi this construction, when opera tion,-the extreme lower end the insulator extends beyond the sides lW' er bore or chamber 7. Upon compression at the engine piston, any carbon or short-circuiting material is thrust against the saidextreme-lower end of the insulator.

Referring to the upper exposed portion of the insulator, it wilt be seen that the upper portion 28 of the electrode passes a considerable' distance within the relatively large bore 24, the lower enlarged portion 29 of the said electrode member being in contact with the insulator only at the lower portion of said member. 'lVhen the two parts ofthe electrode are threaded together and preferably cemented in. position, the upper portion ofthe electrode member 28 is out of contact with the said insulator, and consequently current passing into the upper. elec-- trode member 28 does not'come in contact with the outer exposed portion of the insulator.- Itis therefore impossible to effect a leakage of. current fromv the top of the electrode member 28 over the outside surface of top of the insulator to the metal shell of the P ug- I Referring again to the slotted or cut electrode arranged to exert a capillary attraction for: liquids bridging or binding to bridge the spark gap, it maybe said that this slotted or cut construction of the electrode presents advantages over a tubular electrode. from the standpoint of manufacture, and further presents the very material advantage that in the tubular construction of the electrode there is always present the possibility of a small quantity'of air becoming trapped in the tubular electrode to prevent the capillary action of the same.' 7 With the slotted cut construction of the electrode, the slot or out being open its entire length, all possibility oftrapping air in the slot or cut is entirely eliminated, and thus capillary action of the slot or cut is at all time assured. A further advantage of slotting the electrode either wholly or partially therethrough, is that a greatly increased heated surface is thereby provided to the extent'that the formation of carbon thereon is prevented: 4

The lower internal bore or ch niber 23, through the center of which or 'lcentral electrode 26, forms the lower portion oh the insulation into an insulating wall having annular chambers 20 therein, the planes of the annular chambers being crossed by the said lower internal bore or chamber 23. This construction provides for heating the lower portion of the insulator inte nally as well as externally, and presents alternate portions of large and small cross sectional areas, a large cross sectional. area of the wall being below or under a small cross sectional area. This low-er portion or wall of the insulator having no central portion or core, and out ofcon act with the coating or of an accumulation of carbon to short-circuit the plug. This action may be increased -or diminished according to the nuniberot annular chambers employed and the depths of the same. The deeper the annular chambers and the less the cross sectional areas between their bottoms and the central chamber which crosses their planes, the greater is thethrottling'action on the conduction of the heat. However, the depth of the chambers should be such as to leave a sufficient cross sectional area between the bottoms of these annular chambers and the wall of the central chamber to insure ample mechanical strength at these points; while tlie'width of the annular chambers should be such as not to necessitate an undue length to the chambered portion of the insulator. l5 disposing the lower iuclosed portion of the insulator within the enlarged cham ber 6,:the diameter of the lower inclosed portion-0t the insulator including the depths of the annular chambers, the size of the central chamber 23, and the thickness of the wall between the central chamber 23 and the annular chambers 20, are not limited to av size as will enter the lower threaded portion 9 of the shell I have found this feature to be of great advantage, as this construction permits a wide latitude as to size, diameter and detailed design of the tdwcr chambered portion of the insulation, which would otherwise be restricted it said chambered portion extended down into the lower bore 7 of the threaded portion 1) of the shell, since said threaded portion 9 must be standardized to fit the standardized openings in motors.

Having thus fully described the invention what I claim as'new and desire to secure by Letters Patent of the United States, is:

1. A spark-plug comprising an insulating core, a metal shell and a plurality of elee-' trodes includin a central one said electrodes being separated to provide aspark gap, the said metal shell being provided with an enlarged upper chamber and a smaller lower chamber, the said insulating core being of greater diameter than the said lower chamber and extending into said metal shell providing an annular space between the outer surface'of the insulating core and the inner surface of the wall ofsaid enlarged the central electrode of the plug, said longitudinal bore crossing'the planes of the annular chambers, the outer portion of the insulating core being provided with a relatively large central longitudinal bore, the.

wall of which surrounds but is out of contact with the. upper portion of the central electrode in such manner that the central electrode is out of contact with the top and outer surface of the insulatingcore, one of said electrodes being provided at the spark gap with a capillary slot or cut open at the side of the electrode to exert a capillary attraction for liquid bridging the spark gap. 2. A spark plug comprising an insulating core, a metal shell and a plurality of electrodes, said' electrodes being separated to provide a spark gap, the said metal shell being provided with an enlarged upper chamber and a smaller lower chamber, the said insulating core being of greater diameter'than the said 'lower chamber and extending into said metal shell providing an annular space between the outer surface of the insulating core and the inner wall of said enlarged upper chamber, the said insulating core being provided within said upper enlarged chamber with a plurality of deep and relatively narrow annular chambers, the chambered portion of the insulating core being wholly contained within the said enlarged upper chamber of the metal shell.

A spark plug comprising'an insulating core a metal shell and a plurality of electrodes including a central one and terminal connections, sai'd electrodes being separated to form a spark gap, the lower external, portion of said insulating core being annularly chambered and internallyprovided with a deep and relatively large bore, thew-all of which surrounds but is out of contact with 'the lower portion of the central electrode, ,said bore crossing the plane of the annular chamber in said annularly chambered insulating core, the upper portion of the insulating core being provided with a deep and relatively large bore in such manner that the central electrode, and terminal connections are out of contact with the top and outer surface ofthe insulation.

4. A spark plug comprising an insulating core, a metal shell and a'plurality of electrodes, said electrodes being separated to form a spark gap,'the said metal shell being provided with an enlarged uppercha her and a smaller lower chamber, the said low and between saidannular external f 14sec j insulati'ng. core being; of greater diameter than the said lower c amber and extending into said metal shell providing an annular Gore being provided within. said upper en-v spaoebetween the outer surface of the insulatingro're and the inner wall of said en-' larged upper chamber, the said insulating larged chamber with a plurality of deepand relatiwaly narrow annular chambers, and

also f rovided with a central longitudinal chain. 1', the wall of whic a ber roju'nds'but is positively out of contact with upper chamber of the rovide a spark gap, the'said metal shell in'g provided with an enlarged upper chamberanda-smaller lower chamber, the said insulating core being. of greater diame-' ".ter than the said lower chamber and exten i 'into said metal shell, providing an an nu arspace'between the outer surface of the insulating core and the inner Wall of the said-enlarged upper chamber, the said insulating core being nular chambers one above the other, and

providedwith an internal chamber to freely receive heat'from 'a motor for positively I heating the'interior of the lower portion of 1 the-insulator, said internal. chamber crossingthe planes of the externalannula'r chambersi and-fformingan insulating wall positively separated from and out of'contact Ywith'thecent'ral electrode, the cross sectional '.;areas of said wall at the" planes of the annular external annular chambers being less than the cross sectional areas of-the wall bet chambers,'in such manner that. heat. enteringthe internal chamber and'the annular "eirternal' chambers and imparted to; the lower; portion of the insulator, is dammed j -i'ni sai lower portion and its conduction thro'ttledat the "planes of 'the annular external chambers, the chambered portion of the insulating core being wholly contained within the said enlarged upper chamber of the metal shell. r r

-.6. A. spark plu comprisingan insulating core, a metal she 1' and-a. plurality of electrodes, said electrodes being separated to form a spark ga the said metal shell being provided wit. an enlarged upper chambet and a smaller lower chamber, the said insulating core being of greater diameter than the said lower chamber and extending into said metal shell providing an annular rovided within said enlarged ,u per eham er with a plurality of deep an relatively narrow external-an space between the outer surface of the insulating core and the inner wall of the said.

enlarged upper chamber, the said insulating core being provided Within said "upper enlarged chamber with a plurality of deep and relatively narrow external.v annular chambers one above the other, and provided. with an internal-chamber'to freely receive'heat from a motor for positivelyheating the interior of the'lowerportion of the insulator said internal chamber crossing the planes or thesaid external annular 'chambers, thewholeforming an insulating wall positively separated from and out of contact with the central electrode, the said'external annular chambers one above theother in the said wall, providing alternately large and small cross sectional areas in send wall, in such manner that heat entering, the nternal.

chamber and the external annular chambers and thereby imparted to the-lower portion of the insulator, is dammed in the said areas of large cross section and its conduction throttled at the said areas of small cross section, the chambered-portion of the in sulating core bein Wholly contained within the said enlarged upper chamber of the metal shell.

7. A spark plug comprising a plurality of i electrodes separated to form a spark gap,

one of said electrodes being provided at the spark gap with a capillary slot entering the electrode at the side thereof to attract.

by capillarity a bridge of liquid across the spark gap. v

8H4 spark plug comprising a plurality of electrodes separated to form a spark gap,

and. a capillary opening at the spark gap in one of said electrodes lying longitudinally of the electr'ode'to form an elongated apers ture in the side wall of the electrode to prevent the bridging of the spark gap.

9. A spark plug comprising a plurality of electrodes separated'to form a spark gap, one of said electrodes being provided at the spark gap with. a capillary slot entering the electrode from the side thereof to attract vby capillarity a bridgeof liquid across the spark gap, said capillary slot being positioned in relation to the sparkgap to drain excess oil from the slot by gravity.v

10. A spark plug comprising a plurality of electrodes separated to form a spark gap, and a capillaryppe'ning at the spark gap lying longitudinally of one electrode to pro= vide an elongated aperture in the side of the electrode to attract liquid at the spark gap to prevent the bridging of the spark gap,

said capillary opening being positioned in relation to the spark gap todrain excess oil from said capillary opening-by gravity.

11. A sparlr plug comprising an insulating core, a metal shell. and a plurality'of electrodes, said electrodes being separated to provide a spark gap, the said metal shell upper enlarged upper chamber with a plurality of deep and relatively narrow 'annular external chambers one above the other,

the said chambered portion of the insulating core being wholly contained within the said enlarged upper chamber of the metal shell, the said insulating core being provided with an internal chamber to freely receive heat from a motor to positively heat 'the interior of the said lower portion of the insulator, the insulator forming a wall around the internal chamber positively separated from and out of contact with the central electrode, the cross sectional areas of said wall at said annular external {chambers providing restricted cross sectional areas intermediate the extremities of said internal chamber, in such manner that the portion ot'said Wall below, eachof said external annular chamvhers is of greater cross sectional area than the cross sectional areas at the external annular chambers; whereby heat entering the internalchamber and received by the said Wall, is dammed in the said areas of greater cross section and its conduction throttled at the areas of restricted cross section.

12. A spark plug including a central electrode and a ground electrode, the ground electrode having in its outer Wall a capillary slot open its entire length and presenting an elongated aperture lying in the outer wall of'the ground electrode and longitudinally thereof, the end of the said central electrode terminating adjacent the said capillary slot in the ground electrode to form a spark gap bridge of liquid formed across the spark gap.

18. A spark plug comprising a ground electrode and a central electrode, saidground electrode being provided with acapillary slot cut into the side-of the electrode and substantially parallel therewith, the said slot being positioned With relationeto' the end of the central electrode to form a spark-gap between the end of the central electrode'and' the slotted ground electrode at the saidslot therein and intermediate the. ends ofrthe ground electrode.

14:. A spark plug comprising a ground electrode and a central-electrode, theground electrode being provided along its Wall with a capillary slot cut into the outside-of the wall and extending in a-direction substan tially parallel with that portion of the electrode in which the slot is-cut,'th,e' said slot the electrode being positioned with rela'--' tion to the central electrode to form a spark, gap between the end of the central electrode and the slotted ground electrode at the said .slot therein.

In testimony whereof I aflix'my signature. CHARLES HUGH DUFFY. 

